Microbes living under ice sheets in Antarctica and Greenland could be churning out large quantities of the greenhouse gas methane, a new study suggests.
In recent years scientists have learned that liquid water lurks under much of Antarctica’s massive ice sheet, and so, they say, the potential microbial habitat in this watery world is huge. If the methane produced by the bacteria gets trapped beneath the ice and builds up over long periods of time — a possibility that is far from certain — it could mean that as ice sheets melt under warmer temperatures, they would release large amounts of heat-trapping methane gas.
Jemma Wadham, a geochemist at the University of Bristol in England, described the little-known role of methane-making microbes, called methanogens, below ice sheets on March 15 at an American Geophysical Union conference on Antarctic lakes.
Her team took samples from one site in Antarctica, the Lower Wright glacier, and one in Greenland, the Russell glacier. Trapped within the ice were high concentrations of methane, Wadham said, as well as methanogens themselves — up to 10 million cells per gram in the Antarctic sample and 100,000 cells per gram in Greenland. That’s comparable to the concentration of methanogens found in deep-ocean sediments, she said. The species of microbes were also similar to those found in other polar environments, such as Arctic peat or tundra.
The team then put scrapings from both sites into bottles and incubated them with water to see which microbes might grow. For the Antarctic samples, Wadham said, “nothing happens for 250 days and then bam! You get tons of methane.” The Greenland samples haven’t been growing for as long and so far don’t show much signs of giving off methane — but perhaps they just need more time, she reported at the meeting.